The current success in treating a number of types of childhood cancer is the result, in large part, of therapeutic research conducted by the cooperative pediatric cancer groups. Because most childhood cancers are rare, it is only through this mechanism that adequate numbers of patients can be accrued in reasonable lengths of time and that therapeutic questions can be answered. We will participate in the pediatric division of the Southwest Oncology Group (SWOG) so that our patient population can be used to answer treatment questions which would be impossible to answer were we to conduct only single institution studies. There are some pediatric solid tumors for which the accrual, even in cooperative groups, is insufficient for meaningful therapeutic studies to be conducted. However, a number of intergroup studies are presently active and we plan to participate in these studies through the pediatric division of SWOG. Specifically, we will continue to enter patients on the National Wilms' Tumor Study, the Intergroup Ewing's Sarcoma Study, the Intergroup Rhabdomyosarcoma Study and the Intergroup Hodgkin's Disease Study. The diseases included in these intergroup studies are those which most commonly demand an interdisciplinary approach. We are strongly committed to this approach and have a good working relationship with the necessary cooperating specialities, including Radiation Therapy, Pediatric Surgery, Neurosurgery and Orthopedic Surgery. As more children enter long-term remissions from their diseases, the identification, treatment and potential for prevention of complications of therapy has become a significant area for research. Our major areas of investigation include population based studies of major complications of radiation therapy and chemotherapy, investigations into the treatment and prevention of varicella-zoster infection in immunosuppressed patients and evaluation of the acute and long-term effects of radiation therapy and chemotherapy on various committed stem cell pools and the peripheral blood and bone marrows.